Preparation of diolefins



Nev. 29, 1945. MARSH 2,389,205 Q PREPARATION OF DIOLE FINS Filed June 28, 1945 Gases.

Light Hydrocarbon Liquid Hydrocarbons Water and Steam Heating Fluid I YINVENTOR. v I BY 9 A TTORNE Y.

Aldehydi yatented Nov. 20, 1945 PRHABATION F DIOLEFINS NatEMu-ah,

Baytown, ard Oil Development Delaware Tex, alclgnor to Standpanw, a corporation 01 Application June as, 1943, Seth] No. 492,502

4 Claims. (0. 280-481) The present invention is. directed to the preparation of dioleflns by the reaction of mono-olefins with aldehydes.

It is an object of the present invention to produce dioleflns bypassing an admixture oi aldehyde and mono-olefin in the vapor phase over a suitable catalyst to obtain conjugated dioleflns.

Other objects and advantages of the present invention may be seen from a reading of the fol-' lowing description taken with the drawing, in which the sole figure is in the form of a flow sheet illustrating a preferred embodiment of the present invention.

Turning now specifically to the drawing, a mono-olefin may be withdrawn from storage vessel I l via line l2; containing a control valve l3 and admixed with an aldehyde withdrawn from storage vessel l4 via line l5, provided with a suitable control valv l6. Line I5 is provided with a mixing chamber I! to insure a thorough mixture of the aldehyde and mono-olefin. Line l8, controlled by valve I9, also discharges into line l5 to allow steam to be added to the mono-olefln-aldehyde mixture if desired.

Line I5 is arranged to withdraw the mixture from mixing chamber l1 and discharge it into chamber 20. Chamber is arranged to contain a catalytic mass and is provided with heating means to control the temperature of the catalyst. To insure effective use of the catalyst and maintenance of the desired temperature of the catalyst, a plurality of vertically arranged tubes 2| are positioned within chamber 20 with an upper tube sheet 22 and a lower tube sheet 23 to maintain the tubes in position and define a zone into which the heating medium may be injected for heating the exteriors of'the tubes. Catalytic material 24 is placed in each of tubes 2| with a screen or other suitable arrangement 25 in the lower end of each tube to maintain the catalytic mass in position. The exterior of the tubes may be surrounded by a suitable heating medium such as hot flue gases or mercury vapors which may be circulated by means of inlet 26 and outlet 21.

It has been found that the catalyst 24 employed for contacting the reacting materials should have the characteristics of promoting condensation and dehydration. The catalytic mass should be maintained in the temperature range of 500 to 750 F. Activated alumina and phosphoric acid are particularly useful catalysts in carrying out the reaction of the present invention, but other catalysts having the characteristics of promoting both condensation and dehydration may also be employed. When activated alumina is employed as the catalyst it is desirable to maintain it at a temperature of approximately 650 F., while if a phosphoric acid catalyst is employed it is desirable to maintain it at a temperature of approximately 750 F.

The activated alumina may be prepared by precipitating aluminum hydroxide .from alu-. minum salt solutions with alkali, washing the hydroxide and drying at .300" C., followed .by washing the alinnina free from adsorbed alkali and other salts and redrying. Other well known methods of preparing activated alumina will suggest themselves to the skilled worker.

The phosphoric acid catalyst employed in the process of the present invention may be prepared in accordance with the disclosures of Ipatiefl' and Schaad in U. S; Patent No. 2,275,182.

The products of the reaction otthe aldehyde andmono-olefln in the presence of the catalyst mass 'may be withdrawn from vessel 20 via line' the light diolefins may be withdrawn from the lower portion of settling chamber 34 through line 35, while the low boiling gases may be withdrawn from the settling chamber through line 36. Usually the major portion oi the gases withdrawn through line 88 will consist of hydrogen and carbon monoxide produced by the cracking of aldehyde in the reaction zone.

It will be understood that any suitable aldehyde or mixture of aldehydes may be employed in the reaction of the present invention, and likewise any suitable mono-olefin may be used. Particularly good results have been obtained using formaldehyde as the aldehyde and mono-olefins of the character of isobutylene, butylene-Z, propylene and trimethylethylene either alone or in admixture as the mono-olefin in th reaction.

The production of 'dioleflns by the reaction of an aldehyde and a mono-olefin ma be represented by the following example, in which formaldehyde is employed as the aldehyde or the reaction and isobutylene as the mono-olefin:

CH1, 0 m t CH: cnr-b= oni+n n' U GHF-CH=CH2+HIO whileldonotwishtobeboundbythetheory the sequence of reactions which may be represented by the following equation:

of 1.9 mole of formaldehyde per pound of alumina per hour. The yield of coniugatcd diolenne was 21 weight per cent based on the formaldehyde charged, with the remaining products including other hydrocarbons, hydrogen and carbon monoxide. 7

7 Example 3 A vaporized mixture composed of isobutylene. formaldehyde and steam, in which the mol ratio of isobutylene to formaldehyde was maintained 7 at 4.4 to 1 and the mol ratio of steam to formaldehyde was maintained at 8.4 to 1, was passed over phosphoric acid catalyst heated to 750 F. at the rate of 9.4 mole of formaldehyde per pound of phosphoric acid catalyst per hour. The yield of conjugated dioleflns was 14 weight per cent It will be understood that the above postulated series of steps are carried out in one step in the presence of a heated catalyst and that the suggested intermediate-products are not present in the materials withdrawn from the reaction zone.

The following examples are given to show the yields which may be obtained under actual operating conditions. In each of the following examples the pressure of the reactants was maintained at approximately one atmosphere in the reaction zone.

Example 1 A vaporized mixture composed of isobutylene. formaldehyde and steam, in which the mol ratio of isobutylene to formaldehyde was maintained at 4.2 to 1 and the mol ratio of steam to formaldehyde was maintained at 3.1 to l, was passed over activated alumina heated to 650 F. at the rateof 1 mol of formaldehyde per pound of alumina per hour. The yield of conjugated dioleflns was 17 weight per cent based on the formaldehyde charged. Other reaction products included hydrocarbons, hydrogen and carbon monoxide. Y

Example 2 A aporized mixture composed of propylene. formaldehyde and steam, in which the mol ratio of propylene to formaldehyde was maintained at.

3.1 to 1 and the mol ratio of steam to formaldehyde was maintained at 3 to 1, was passed over based on the formaldehyde charged, the remaining products of reaction including other hydrocarbons, hydrogen and carbon monoxide.

Having fully described and illustrated the practice of the present invention, what I desire toclaim is:

1. A method for producing dioleflns comprising the steps of contacting an admixture of isobutylene and formaldehyde in vaporized .form

with activated alumina maintained at a temperature of approximately 650 F'., removing the resulting fluid from contact with said activated alumina, cooling and separating dioleflns therefrom.

2. A method in accordance with claim 1 in which steam is admixed with the isdbutylene and formaldehyde contacted with said activated alumina. s

3. A method for producing dioleflns comprising the steps of contacting an admixture of monoolefln and aldehyde with activated alumina at a temperature within the range of 500 to 750 F. to cause the formation of dioleflns, removing the products of said reaction from contact with said catalyst and separating the dioleflns therefrom.

4. A method for producing diolefins comprising the steps of admixing formaldehyde with a mono-olefin, passing said admixture over activated alumina maintained in the temperature range of' 500 F. to 750 F., withdrawing said activated alumina heated to 642 F. at the rate fluid mixture from contact with said catalyst,

cooling and subsequently separating dioleilns therefrom.

NAT H. MARSH. 

